Hach-Lange LZV936 - DR 6000 Brewery Analysis software - Handbuch (Seite 31)

English 31
Procedure for reducibility
1. Prepare the blank values and samples according to the work
procedure.
2. Select STORED PROGRAMS > SELECT BY NUMBER.
3. Enter the number 2004 for the program "Reducibility". Confirm with
OK.
4. Press START to start the program.
5. Enter the blank value (see sample preparation) and press ZERO.
6. Insert the analysis cuvette with the prepared sample. After 60 sec
press READ.
The result is shown on the display.
Note: To analyze further samples, repeat the procedure from step
5, that means each sample requires a specific blank value.
Anthocyanogens (Harris and Ricketts method)
Anthocyanogens (leucoanthocyanidins) are phenolic compounds that
are transformed by hot hydrochloric acid into red-colored
anthocyanidins. Amount and condensation- or polymerization degree of
these compounds have an influence on the formation of colloidal
turbidities in the beer. Stabilization measures with PVPP correlate to a
reduction of the anthocyanogen content.
Principle
The anthocyanogens are adsorbed to polyamide, the adsorbate
dissolved in butanol-hydrochloric acid and heated, whereby a red-
colored solution ensues, whose intensity is measured photometrically.
Application area
Beer, wort
Measurement range
0–100 mg/L
Accessories
• Shaking machine
• Centrifuge
• Mixing flask with ground-in stopper, 50 mL
• Frit 1 G4
• Filter flask
• Reagent flasks with ground-in stopper, 30 mL, graduation up to
25 mL
• Vacuum pump
• Spectrophotometer, 550 nm
• 10 mm rectangular cuvette OS
Reagents
• MN-polyamide SC 6
• Solution 1: n-Butanol / 37 % hydrochloric acid 5+1 (V/V)
• Solution 2: Dissolve 120 mg iron(II) sulfate (FeSO
4
x 7 H
2
O) in
100 mL solution 1
Sample preparation
1. Centrifuge worts and young beers for 10 min at 3000 rpm.
2. Pipette 5 mL beer (or wort) + 5 mL dist. H
2
0 in a 50 mL mixing
flask.
3. Pipette 10 mL dist. H
2
O (blank value) in a 50 mL mixing flask.
4. Rinse 0.5 g polyamide powder with 10 mL dist. H
2
O in the mixing
flask.
5. Mechanically shake the two mixing flasks for 40 min.
6. Filter each of the suspensions through a 1 G4 frit and rinse twice
with approximately 20 mL dist. H
2
O.
7. Vacuum the frits and polyamide powder dry, transfer the residue
respectively with a spatula quantatively into the reagent flask and
purge with 15 mL of solution 1.